Means for separating undesired from desired electric currents



Ma ly 20, 1930. GAGE 1,758,940

MEANS FOR SEPARATING UNDESIRED FROM DESIRED ELECTRIC CURRENTS Filed Feb.6, 1924 7 .c AMHMLAMAm D 1 ML 1 lhhiuluinik f f y INVENTOR.

Patented May 20, 1930 I UNITED STATES PATENT, OFFICE EDWARD G. GAGE, OFNEW YORK, N. Y., ASSIGNOR TO RADIO CORPORATION OF AMERICA, OF.NEW YORK,N. Y., A OORIPORATION OF DELAWARE MEANS non sErARAriNennnnsIiaEnFROM'DESIRED nnnc'rnrc CURRENTS,

Applicationfiled Fetruaryfi, 1924. Serial No. 690,947.[

This application is a continuance in part of my prior application SerialNo. 463,072, filed April 20, 1921.

In the art of radio telegraphy and telephony, it is found that naturaldisturbances in the ether interfere with the reception of intelligence.

' The object of this invention is to eliminate such disturbances. I

Heretoforeit has been common'practice to provide receiving circuits inopposition in which a broadly tuned wave suchas the natural orhereinafter'called undesired electric currents were made to cancehwhilethe 1 signal or hereinafter called desired current,

of a sharply tuned wave wasretainedby detuning one of the circuits. 7

Such interference preventers act as cur rent limitersby'reducingundesired currents 2 to the level of the signal.

This invention relates to a methodof raising the level of the signal ordesired current above that of the stray or undesired current.

The principle on whichmy system Works depends on the difierenti'atingbetween what may be termed decrement bands of signal and stray, theWidth of each respective band being shown as the base of the impulseresonance curve. A plurality of these bands be ing combined, thealgebraic sum consists only of signal or desired-currents as regardsamplitude owing to phase' character stics of each impulse. 1 l 7 Toaccomplish this, I-providetwo suchsys terns, eachwith opposed detecto'rsand selec tive means, and combine the results m; a 7

common receiving'circuitflas'shown,

Each system receives one of two different waves sent out from atransmitter with a common modulator,as shown in Fig. My invention will:best beunderstood by those skilled in the art by reference to thefollowing description "taken in connection with the accompanyingdrawings, in which,

Fig. 1 represents a transmitting system for radio telephony ortelegraphy-having two separate antennae, each emitting a dlstinctlydifierent wave length, but modulated simultaneously by a commonmodulator. 7

60 Fig. 2 represents a receiving system comprising four separate antennasystems divided into two sections,each section consisting of receivingcircuits in opposition, tuning devices for selecting the desiredreceived currents from the undesired currents of each section, and atransformer with windings for combining the desired currents andtransferring them to the amplifier and telephone.

Fig. 3 represents undesired or static impulses combined with desired orsignal impulses and opposed to various combinations of desired andundesired currents, as hereinafter described. V

In the system described, in Fig. 1, the antennae 1 and 2 are excited bythe vacuum valve oscillators 3 and l and each oscillator is modulated bythe modulating circuit 5 in which a microphone or key is included.

As an example of thewave lengths emitted by the antennae, it isconvenient to specify 2,000 meters for antenna 1, and 3,000 meters forantenna 2, although the system is not limited to thiscombination; i

In Fig. 2 the .four receiving antennae 6, 7, 8 and 9 are connected asfollows:

Antenna 6 has connected to it by close coupling, 10 a detector 14shownhere as a magnetic detector because that type is peculiarly adaptedfor the purpose, but it is to be understood that other detectors such asvacuum valves or crystal detectors may be used without departing fromthe scope of the invention. Y

Antenna 7 is similarlto antenna 6 except :that its 'coupling'isinductive and loose.

Antenna systems 8 and 9 are respectively the same as? andffir f j Thetransformer 18 haswound upon it in conjunction the two output circuitsfrom detectors l4 'and1'5 in opposition and 16 and 17 in opposition, andthe input circuit 21 of thevacuum valve amplifier 22. The outputcircuitofwhich is led'to'the telephone 23.

curves of undesired and desired currents respectively; V p C and Drepresent rectified desired and undesired currents present in 14 and 17respectively' f fl and F- representtherectified desired and Fig. 3 -Aand B represent decrement undesired currents present in 19 and 20respectively, after being acted upon by 15 and 16 in opposition.

G represents the rectified desired currents resulting from combining Cand E in conjunction, and shows the signal or desired eurrent level Habove the stray or undesired current level J.

In operation, the transmitter is caused to emit the two sharply tunedwave lengths of 2,000 and 3,000 meters respectively.

Strays or undesired currents are of both high and low decrement. Thosecurrents of high decrement will tune broadly, while those of lowdecrement tune sharply. Desired currents of both 2,000 and 3,000 meterswave length tune sharply.

The receiving circuits are adjusted as follows:

Antenna system 6 is tuned to receive the 2,000 meter signal of sharptuning.

Antenna system 7 is then detuned sufiic1ently to eliminate the desired2,000 meter signal, as an example, to 2,100 meters.

Antenna system 9 is tuned to receive the 3,000 meter desired signal ofsharp tuning.

Antenna system 8 is detuned sufliciently to eliminate the desired 3,000meter signal as an example to 3,100 meters.

The result of this operation is as follows:

Antenna system 6 being conductively and tightly coupled, tunes broadly,and at 2,000 meters it receives and detects both desired and undesiredcurrents.

Antenna system 7 being inductively or loosely coupled, tunes sharply,and when tuned to 2,100 meters, the desired signal is eliminated. Theundesired, however, being of higher decrement, is nearly as strong at2,100, as at 2,000 meters. Hence it remains.

Antenna system 9 being conductively coupled, tunes broadly, and receivesand detects both desired and undesired signals at 3,000 meters.

Antenna system 8 being inductively or loosely coupled, tunes sharply,and when tuned to 3,100 meters, the desired signal is eliminated, whilethe undesired remains at practically full strength.

The detected currents from 14 and 15 in opposition and 16 and 17 also inopposition, being combined in conjunction, at the transformer 18,produce in the winding 21 only desired currents, and these aretransferred through the amplifier 21 to the telephone 23.

It will be seen that desired signals on both 2,000 and 3,000 metersbeing detected from a common modulator, are in phase, and therefore add,while strays or undesired currents, when of a decrement as low as thesignal, appear in only one detector, and where different stray impulsesare present, they are not in phase.

In place of the telephone 23, the input circuit of a system described byme in a previous application, (U. S.) Serial No. 463,07 2, filed April20, 1921, may be connected in which a detector is caused to becomefatigued by the desired signal, allowing opposed but constant detectorto register the signal.

While for the sake of olearness, I have described the application of myinvention to a system of elemental design, it will be apparent to thoseskilled in the art, that it may also be applied to systems in whichradio frequency amplifiers are inserted before the detectors in thecustomary manner and that numerous applications thereof may be madewithout departing from the scope of the appended claims.

VVhat I claim is:

1. In radio signalling, the method of receiving a plurality of waves ofdifferent frequencies subject to disturbance currents, which consists inseparately receiving each frequency with its disturbance currents,combining with each frequency in opposite phase relation a portion ofthe disturbance currents, combining in the same phase relation thecurrents so obtained and utilizing the result-ant currents.

2. In a radio signalling system, the method of combining a plurality ofreceived frequencies each subject to disturbance currents which consistsin receiving a plurality of signalling frequencies, in eliminating byopposition the disturbance currents accompanying each of the receivedfrequencies, in combining the remaining currents of each of the receivedfrequencies in additive relationship, and in utilizing the resultantcombined currents.

3. In radio signalling systems for simultaneously transmitting andreceiving a plurality of frequencies each subject to disturbancecurrents, means for simultaneously modulating a plurality of transmittedfrequencies, means for receiving each of the transmitted frequenciesseparately combined with a portion of the disturbance currentsaccompanying the same, means for eliminating the disturbance currentsaccompanying each of the independent received frequencies by opposition,means for combining received currents of each of the independentfrequencies in additive relationship, and means for utilizing theresultant combined currents.

Signed at New York in the county of New York and State of New York this5th day of February, A. D. 1924.

EDWARD G. GAGE.

